[mythtv-users] Linux software raid question

Gerald Brandt gbr at majentis.com
Thu Jun 5 17:08:09 UTC 2008

----- "Ian Clark" wrote: 
> 2008/6/5 Gerald Brandt : > I've been running a 5x250 software raid5 array for a few years. It's easy > to setup and maintain and uses very little CPU. If I had the cash, I'd prob > convert to hardware raid5, and buy 2 controllers (1 spare). > > Sadly, I don't have the cash, so my biggest decision now is: when I build a > new system, do I go software raid 5 or software raid 6? > If cash is an issue then you need to look at how likely you are to have more than 1 drive fail at any given time. How many failures have you had in the last few years? How many drives are you planing on RAIDing? The more drives the more likely to fail. How important is the data? How regular do you backup? (EG, I have a RAID 5 array, that I can't afford to backup, so I'm more reliant on the redundancy as I really don't want to loose data.) If you're building a box just for storage Suns ZFS looks really good, and it does solve some of the problems in software that you would otherwise need a hardware RAID card for (or much reduced performance). It's also easy to admin and fairly scalable. However, this does mean a move to Solaris (or Nexenta; which is GNU based), and learning a new (similar) system isn't everyone's idea of fun. Aside: As there seem to be a lot of linux RAID experts round here, how critical is the number of discs in a linux RAID 5 array? I've got a 4 disc RAID 5 array on NetBSD, but I suffer from performance issues (as the number of discs is not a power of two + 1), but I'm wondering if linux is more flexible in this regard. (NetBSDs FFS needs a block size that's a multiple of 2, so tuning stripe size and block size to ensure a full stripe write whenever possible is not possible with 4 discs.) Ian 
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I've had no failures on my current 5x250 raid5 system, and I do back up the critical stuff. Myth is non-critical, and it takes most of the array. 

I'll be starting with a 3x1 TB raid 5, I think, and then adding 1 TB drives as I need them. 

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